Boxing great Muhammad Ali has paid a moving tribute to his one-time adversary Sir Henry Cooper, who died on Sunday.

The British fighting legend and charity advocate passed away at his son's home in Surrey, England after a short battle with ill health, two days before his 77th birthday.

Sir Henry famously knocked down a cocky young Ali, then Cassius Clay, in 1963 -- a punch which he went on to say "hit me so hard my ancestors in Africa felt it." Ali went on to win the fight and the pair became lifelong pals.

After hearing of his death, the 69-year-old fondly remembered Cooper and passed on his condolences to the beloved Brit's family in a touching statement.

"Henry always had a smile for me; a warm and embracing smile. It was always a pleasure being in Henry's company," Ali said.

"I will miss my old friend. He was a great fighter and a gentleman. I was not aware he was ill. I visited with him two summers ago during a brief visit. He was in good humour and looked quite fit.

"My family and I extend our heartfelt sympathies to his family and loved ones."